Stabilization of radiopharmaceutical compositions using hydrophilic 6-hydroxy chromans

ABSTRACT

Radiopharmaceutical compositions which are stabilized by addition of a hydrophilic 6-hydroxy-chroman derivative.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.10/131,346 filed on 24 Apr. 2002 now U.S. Pat. No. 6,881,396, which is acontinuation-in-part of U.S. patent application Ser. No. 09/695,360filed on 24 Oct. 2000 now abandoned, and a continuation-in-part ofInternational Application No. PCT/US 01/50423 filed on 24 Oct. 2001.

This application also is related to commonly assigned U.S. patentapplication Ser. No. 10/131,543, “Stabilization of RadiopharmaceuticalCompositions Using Hydrophilic Thioethers” and to commonly assigned U.S.patent application Ser. No. 10/131,546 “Stabilization ofRadiopharmaceutical Compositions Using Hydrophilic Thioethers andHydrophilic 6-Hydroxy Chromans” both of which were filed on 24 Apr.2002. application Ser. Nos. 10/131,543 and 10/131,546 arecontinuations-in-part of application Ser. Nos. 09/694,992 and09/695,494, respectively, both of which were filed on 24 Oct. 2000 andboth of which are now abandoned.

BACKGROUND OF INVENTION

The present invention relates to novel stabilizers ofradiopharmaceutical compositions used for diagnosis and therapy. Inparticular, the invention relates to use of a hydrophilic6-hydroxy-chroman derivative to increase the shelf-life of diagnosticand therapeutic radiopharmaceuticals.

A number of radionuclides are routinely employed in nuclear medicine,both as diagnostic agents and as therapeutics. For example, ^(99m)Tc,¹¹¹In, ¹⁸F, and ²⁰¹Tl are employed as diagnostic imaging agents, and¹³¹I, ³²P, ⁸⁹Sr, and ¹⁵³Sm are in therapeutic use. In addition, nuclidessuch as ¹⁸⁶Re, ¹⁸⁸Re, ²¹²Bi, ²¹³Bi, ⁹⁰Y, ⁶⁷Cu, ¹⁹²Ir, ¹⁶⁵Dy, and^(117m)Sn have been proposed as potential therapeutic agents. Suchradionuclides are administered in the form of radiopharmaceuticalcompositions, which generally include a chelator for the nuclide.Radiopharmaceuticals may additionally include a targeting molecule suchas a monoclonal antibody, an antibody fragment, or a receptor ligand.The availability of radiopharmaceuticals has significantly advanceddiagnosis and treatment of a variety of diseases.

Chemical decomposition may limit a radiopharmaceutical's shelf life bydecreasing the radiochemical purity of the agent over time. For example,a radiopharmaceutical containing ^(99m)Tc, ¹⁸⁶Re, or ¹⁸⁸Re may besusceptible to oxidation of the nuclide itself. In addition, theradiation emitted from a radionuclide can break chemical bonds of othercomponents of the composition, thus causing autoradiolysis.Autoradiolysis is a particular problem when the radiopharmaceuticalcontains higher energy nuclides, such as β-emitters (e.g., ¹⁸⁶Re, ¹⁸⁸Re,⁹⁰Y, ¹³¹I) and α-emitters (e.g., ²¹³Bi, ²¹²Bi, ²¹¹At, ²²⁵Ac, ²²³Ra).

Thus many radiopharmaceuticals require stabilizers to maximize shelflife. Such stabilizers must be non-toxic and must be able to maintainthe product's radiochemical purity for an acceptable shelf-life as wellas during use. In addition, an acceptable radiopharmaceutical stabilizermust not interfere with delivery of the radionuclide to the target site.

Methods for stabilizing radiopharmaceuticals by adding gentisates aredisclosed, for example, in U.S. Pat. Nos. 4,232,000; 4,233,284;4,497,744; 5,384,113. Stabilization of radiopharmaceuticals usingascorbic acid is disclosed in U.S. Pat. Nos. 5,393,512 and 5,011,676, inWO 97/28181 and in WO 98/33531. Hydroquinone stabilizers ofradiopharmaceuticals is disclosed in U.S. Pat. No. 4,229,427. Othercompounds such as reductic acid, erythorbic acid, p-aminobenzoic acid,4-hydroxybenzoic acid, nicotinic acid, nicotinamide,2,5-dihydroxy-1,4-benzenedisulfonic acid, tartaric acid, inositol, andthe like, have also been used to stabilize radiopharmaceuticalcompositions.

U.S. Pat. No. 5,384,113 discloses a method of preventing autoradiolysisof peptides radiolabelled with ¹¹¹In using gentisic acid or gentisylalcohol. In addition to preventing autoradiolysis of peptides by ¹¹¹In,the method of U.S. Pat. No. 5,384,113 is proposed to preventautoradiolysis of peptides by ⁶⁷Ga, ¹⁶⁹Yb, ¹²⁵I, ¹²³I, and ²⁰¹Tl. Tworadiolabelled peptides, ¹¹¹In-DTPA-octreotide and ¹²³I-LHRH, were testedfor autoradiolysis prevention. A monoclonal antibody, NR-Lu-10, labelledwith ¹⁸⁶Re was also specifically exemplified.

As indicated in Example 1, infra, the present inventors have found thatthat when added as a component in radiopharmaceutical kit formulations,gentisic acid decreases the radiochemical purity of some^(99m)Tc-labelled peptides, and thus is not useful as a stabilizer ofsome radiolabelled peptides. A need exists, therefore, for additionalstabilizers of radiopharmaceuticals. A particular need exists forstabilizers of radiopharmaceuticals containing less than 70 amino acidslinked by peptide bonds.

U.S. Pat. Nos. 3,947,473, 4,003,919, 4,018,799 and 4,026,907 disclose avariety of antioxidant hydrophilic 6-hydroxy-chroman compounds asintermediates in preparation of optically active α-tocopherol. U.S. Pat.No. 4,511,685 discloses hydrophilic 6-hydroxy-chroman derivatives anduse of such derivatives to stabilize polypropylene compositions. U.S.Pat. Nos. 4,847,267 and 4,970,216 disclose use of one such hydrophilic6-hydroxy-chroman, 6-hydroxy-2,5,7,8-tetramethyl-2-carboxylic acid aloneor in combination with sulfur compounds, including glutathione orcysteine, as a skin treatment composition to inhibit generation of freeradicals in the skin.

SUMMARY OF THE INVENTION

It has now been surprisingly found that the radiolabelling efficiencyand shelf-life of peptide and non-peptide radiopharmaceuticalcompositions may be significantly increased by addition of a stabilizingamount of a hydrophilic 6-hydroxy-chroman derivative.

In one embodiment, the invention provides a composition comprising aradiopharmaceutical precursor and a stabilizing amount of a hydrophilic6-hydroxy-chroman devirative.

In another embodiment, the invention provides a method of stabilizing aradiopharmaceutical comprising the steps of:

a) combining a precursor of said radiopharmaceutical with a stabilizingamount of a hydrophilic 6-hydroxy-chroman derivative in a container; and

b) adding a radionuclide to the container.

In a further embodiment, the invention provides a kit comprising asealed vial containing a predetermined quantity of a radiopharmaceuticalprecursor and a stabilizing amount of a hydrophilic 6-hydroxy-chromanderivative.

DETAILED DESCRIPTION OF THE INVENTION

The patent and scientific literature referenced herein establish theknowledge available to those with skill in the art. The issued U.S.patents are hereby incorporated by reference.

As defined herein, a “radiopharmaceutical” or “radiopharmaceuticalcomposition” comprises a radionuclide, a chelator, and optionally atargeting moiety or domain.

In accordance with the invention, a “precursor” of a radiopharmaceuticalis defined as comprising an unlabelled, that is, non-radioactive,reagent which may be a chelator or a chelator covalently linked to atargeting moiety or domain.

A “targeting moiety or domain” as defined herein as a moiety or domaincapable of binding specifically to a site within a mammalian body suchas a receptor on a cell surface. Targeting moieties or domains withinthe scope of the present invention include but are not limited toantibodies, antibody fragments such as Fab or F(ab)′₂ fragments, epitopebinding complementarity determining regions derived from antibodies,peptides, growth factors or receptor binding fragments thereof,hormones, steroids, receptor binding nucleic acids, receptor bindingcarbohydrates including monosaccharides, disaccharides, andoligosaccharides, receptor-binding lipids, benzodiazepines, receptorbinding antibiotics, and the like.

A “stabilizing amount” is defined herein as that amount of hydrophilic6-hydroxy-chroman sufficient to maintain the radiochemical purity, asmeasured by known methods such as those disclosed in the examples below,of a radiopharmaceutical composition relative to that of theradiopharmaceutical composition without the additive for at least 3hours. Preferably, a clinically acceptable radiochemical purity for aradiopharmaceutical is at least 80% of the labelled undegradedradiopharmaceutical. More preferably, a clinically acceptableradiochemical purity for a radiopharmaceutical is at least 85% of thelabelled undegraded radiopharmaceutical. Most preferably, a clinicallyacceptable radiochemical purity for a radiopharmaceutical is at least90% of the labelled undegraded radiopharmaceutical.

A “hydrophilic 6-hydroxy-chroman derivative” is defined in accordancewith the present invention as having a formula:

wherein

-   one of Y and Z is selected from the group consisting of O, S, C═O,    and (CHR³)_(n) where n is an interger from 0 to 3, and the other of    Y and Z is selected from the group consisting of C═O and (CHR³)_(n)    where n is an integer from 0 to 3;-   each R³ group is independently selected from the group consisting of    H, alkyl, halogen, —OR⁴, —SO₃H, —SO₃R⁴, —S(O)mR⁴, —COOR⁴, —NO₂,    —CONH_(m)(R⁴)_(2-m), —NH_(m)(R⁴)_(2-m), —COR⁴, —CH₂OR⁴, —COR⁵,    —SO₂NH_(m)(R⁴)^(2-m), —R⁵, and —CH₂R⁵, where m is an integer from 0    to 2;-   R⁴ is H or C₁ to C₃ alkyl; and-   R⁵ is selected from the group consisting of a monosaccharide, a    disaccharide, and a hydrophilic peptide sequence of up to 5 amino    acids comprising at least one hydrophilic amino acid residue.    Preferably, Y is (CH₂) and Z is (CH₂). Exemplary hydrophilic    6-hydroxy-chroman derivatives of the present invention include    6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox®,    available from Aldrich Chemical Co., (Milwaukee, Wis., USA);    6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid-4-sulfonic    acid; 6-hydroxy-2,5,7,8-tetramethylchroman-3-hydroxy-2-carboxylic    acid; 6-hydroxy-2,5,7,8-tetramethylchroman-2-glucosamine, having a    structure:

and6-hydroxy-2,5,7,8-tetramethylchroman-2-(carboxy-seryl-seryl-serylamide),having the structure:

Preferably, the hydrophilic 6-hydroxy-chroman derivative of the presentinvention is a water soluble vitamin E derivative. More preferably, thehydrophilic 6-hydroxy-chroman derivative of the invention is a6-hydroxy-2,5,7,8-tetramethyl-2-carboxylic acid derivative having —CH₂at the 3- and 4-positions and a hydrophilic substituent at the2-position. Most preferably, the hydrophilic 6-hydroxy-chromanderivative of the invention is6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid.

Any radiopharmaceutical may be stabilized by addition of a hydrophilic6-hydroxy-chroman as taught herein. Ligand-type radiopharmaceuticalswhich do not comprise a targeting moiety or domain, such as Tc 99m MAG3(TechneScan®, Mallinckrodt Medical, Inc., St. Louis, Mo., USA), may bestabilized in accordance with the present invention. In addition,radiopharmaceuticals comprising any kind of targeting moiety or domainmay be stabilized in accordance with the present invention.

Recently a new class of radiopharmaceuticals has been developed whichtarget a radiolabel to a particular tissue, disease site, or organthrough a small receptor-specific molecule, which may be a peptide, aβ-glucan, a benzodiazepine, or other small molecule. Suchradiopharmaceuticals are disclosed and claimed, for example, in commonlyassigned U.S. Pat. Nos. 5,508,020; 5,225,180; 5,405,597; 5,443,815;5,552,525; 5,561,220; 5,620,675; 5,645,815; 5,654,272; 5,681,541;5,711,931; 5,714,579; 5,716,596; 5,736,122; 5,770,179; 5,783,170;5,788,960; 5,807,537; 5,807,538; 5,811,394; 5,814,297; 5,814,298;5,814,299; 5,820,845; 5,820,846; 5,830,856; 5,833,942; 5,843,401;5,843,403; 5,849,260; 5,849,261; 5,851,509; 5,866,097; 5,871,711;5,932,189; 5,951,964; 5,955,426; 5,976,496; 5,997,844; 6,007,792;6,017,509; 6,017,512; 6,028,056; 6,051,206; 6,074,627; 6,086,850;6,171,578; 6,241,965; 6,248,304; and 6,479,032 and in commonly assignedcopending U.S. patent application Ser. Nos. 08/236,402 and 08/253,973.These new agents comprise a chelator covalently linked to thereceptor-specific targeting moiety or domain, and a radiolabel complexedwith the chelator. A kit for making one such agent, ACUTECT®, hasreceived approval in the U.S. for scintigraphic imaging of acute deepvein thrombosis. A second kit, NEOTECT®, has been approved in the U.S.for imaging malignant lung tumors. The stabilizers of the presentinvention are particularly suitable for use with radiopharmaceuticalswhich comprise chelators covalently linked to peptide, β-glucan,benzodiazepine, or other small targeting molecules as described in thecommonly assigned patents and copending applications listed above.

In general, radiopharmaceuticals containing precursors in which atargeting moiety or domain is covalently linked to a monoamine, diamide,single thiol containing chelator such as those disclosed in commonlyassigned copending U.S. patent application Ser. No. 08/253,973 and in WO95/33497 are stabilized using a hydrophilic thioether, a hydrophilic6-hydroxy-chroman or a mixture of a hydrophilic thioether and ahydrophilic 6-hydroxy-chroman in accordance with this invention. Inaddition, radiopharmaceuticals containing precursors in which atargeting moiety or domain is covalently linked to a bisamine bisthiol(BAT) chelator such as those disclosed in commonly assigned U.S. Pat.Nos. 5,780,007; 5,776,428; 5,720,934; 5,922,303; 5,965,107; 6,086,849;and 6,093,383 and in WO 93/21962 may be stabilized in accordance withthe present invention.

The stabilizers of the present invention may also be used forradiopharmaceuticals comprising targeting molecules covalently linked toany chelator, such as the diamine monoamide thiol chelators and thetriamine thiol chelators described in U.S. Pat. No. 5,688,485 and thetriamide thiols disclosed in U.S. Pat. No. 5,091,514.

The stabilizers of the invention are preferably employed to increase theshelf life of radiopharmaceuticals comprising a targeting moietycovalently linked to a peptide metal chelator having a formulaC(pgp)^(S)-(aa)-C(pgp)^(S)wherein (pgp)^(S) is H or a thiol protecting group and (aa) is an aminoacid. Such chelators are disclosed and claimed in commonly assigned U.S.Pat. Nos. 5,654,272; 5,681,541; 5,788,960; and 5,811,394.

The stabilizers of the invention may also be employed to increase theshelf life of radiopharmaceuticals comprising a targeting moietycovalently linked to a peptide metal chelator having a formula selectedfrom the group consisting of:

wherein

-   -   X is H or a protecting group;    -   (amino acid) is any amino acid;        and

wherein

-   -   X is H or a protecting group;    -   (amino acid) is any amino acid.        Such chelators are disclosed and claimed in commonly assigned        U.S. Pat. Nos. 5,720,934; 5,776,428; 5,780,007; 6,086,849 and        6,093,383.

More preferably, the stabilizers of the invention are used to increasethe shelf life of radiopharmaceuticals comprising a targeting moietycovalently linked to a peptide metal chelator comprising a single thiolhaving a formula:A-CZ(B)—[C(R′R″)]_(n)—Xwherein

-   -   A is H, HOOC, H₂NOC, (peptide)-NHOC, (peptide)-OOC or R″″;    -   B is H, SH, —NHR′″, —N(R′″)-(peptide), or R″″;    -   X is H, SH, —NHR′″, —N(R′″)-(peptide) or R″″;    -   Z is H or R″″;    -   R′, R″, R′″ and R″″ are independently H or lower straight or        branched chain or cyclic alkyl;    -   n is 0, 1 or 2;        and    -   where B is —NHR′″ or —N(R′″)-(peptide), X is SH, and n is 1 or        2;    -   where X is —NHR′″ or —N(R′″)-(peptide), B is SH, and n is 1 or        2;    -   where B is H or R″″, A is HOOC, H₂NOC, (peptide)-NHOC,        (peptide)-OOC, X is SH, and n is 0 or 1;    -   where A is H or R″″, then where B is SH, X is —NHR′″ or        —N(R′″)-(peptide) and where X is SH, B is —NHR′″ or        —N(R′″)-(peptide);    -   where X is H or R″″, A is HOOC, H₂NOC, (peptide)-NHOC,        (peptide)-OOC and B is SH;    -   where Z is methyl, X is methyl, A is HOOC, H₂NOC,        (peptide)-NHOC, (peptide)-OOC, B is SH and n is 0.        Such chelators are disclosed and claimed in commonly assigned        U.S. Pat. Nos. 5,443,815; 5,807,537; 5,814,297; and 5,866,097.

Specific embodiments of the single thiol containing radiometal chelatorstabilized in accordance with the present invention are described andclaimed in commonly assigned copending U.S. patent application Ser. No.08/236,402 and in WO 95/29708, and include chelators having the chemicalformula:R¹—CO-(amino acid)¹-(amino acid)²-Zwherein (amino acid)¹ and (amino acid)² are each independently anyprimary α- or β-amino acid that does not comprise a thiol group, Z is athiol-containing moiety selected from the group consisting of cysteine,homocysteine, isocysteine, penicillamine, 2-mercaptoethylamine and3-mercaptopropylamine, and R¹ is lower (C¹-C⁴) alkyl, an amino acid, ora peptide comprising 2 to 10 amino acids. When Z is cysteine,homocysteine, isocysteine or penicillamine, the carbonyl group of saidmoiety is covalently linked to a hydroxyl group, a NR³R⁴ group, whereineach of R³ and R⁴ are independently H or lower (C¹-C⁴) alkyl, an aminoacid or a peptide comprising 2 to 10 amino acids.

Alternatively, a single thiol containing radiometal chelator stabilizedin accordance with the present invention has a formula:Y-(amino acid)²-(amino acid)¹-NHR²wherein Y is a thiol-containing moiety that is cysteine, homocysteine,isocysteine, penicillamine, 2-mercaptoacetate or 3-mercaptopropionate,(amino acid)¹ and (amino acid)² are each independently any primary α- orβ-amino acid that does not comprise a thiol group, and R² is H or lower(C¹-C⁴) alkyl, an amino acid or a peptide comprising 2 to 10 aminoacids. When Y is cysteine, homocysteine, isocysteine or penicillamine,the amino group of said moiety is covalently linked to —H, an amino acidor a peptide comprising 2 to 10 amino acids.

Specific embodiments of the single thiol containing radiometal chelatorare selected from the group consisting of:-(amino acid)¹-(amino acid)²-A-CZ(B)-{C(R¹R²)}_(n)—X},-A-CZ(B)—{C(R¹R²)}_(n)—X}-(amino acid)¹-(amino acid)²,-(a primary α,ω- or β,ω-diamino acid)-(aminoacid)¹-A-CZ(B)—{C(R¹R²)}_(n)—X},and-A-CZ(B)—{C(R¹R²)}_(n)—X}-(amino acid)¹-(a primary α,β- or α,ω-diaminoacid)wherein the term “α,ω-diamino acid” represents an amino acid having anamine on the α carbon atom and an amine on the carbon atom most distalfrom the a carbon atom, the term “β,ω-diamino acid” represents an aminoacid having an amine on the β carbon atom and an amine on the carbonatom most distal from the β carbon atom, and (amino acid)¹ and (aminoacid)² are each independently any naturally-occurring, modified,substituted or altered α- or β-amino acid not containing a thiol group.

Specific single thiol-containing radiometal chelators stabilized inaccordance with the invention have a formula selected from the groupconsisting of: -Gly-Gly-Cys-, Cys-Gly-Gly-, -(ε-Lys)-Gly-Cys-,(δ-Orn)-Gly-Cys-, -(γ-Dab)-Gly-Cys-, -(β-Dap)-Lys-Cys-, and-(β-Dap)-Gly-Cys-. (In these formulae, ε-Lys represents a lysine residuein which the ε-amino group, rather than the typical α-amino group, iscovalently linked to the carboxyl group of the adjacent amino acid toform a peptide bond; δ-Orn represents an ornithine residue in which theδ-amino group, rather than the typical α-amino group, is covalentlylinked to the carboxyl group of the adjacent amino acid to form apeptide bond; γ-Dab represents a 2,4-diaminobutyric acid residue inwhich the γ-amino group is covalently linked to the carboxyl group ofthe adjacent amino acid to form a peptide bond; and β-Dap represents a2,3-diaminopropionic acid residue in which the β-amino group iscovalently linked to the carboxyl group of the adjacent amino acid toform a peptide bond.)

Most preferably, the stabilizers of the invention may be used toincrease the shelf life of radiopharmaceuticals comprising a targetingmoiety covalently linked to a monoamine, diamide, single thiol metalchelator such as those disclosed and claimed in commonly assignedcopending U.S. patent application Ser. No. 08/253,973 and in WO95/33497, and to increase the shelf life of radiopharmaceuticalscomprising a targeting moiety covalently linked to a bisamide bisthiolmetal chelator such as those disclosed and claimed in commonly assignedU.S. Pat. Nos. 5,780,007; 5,922,303; 6,086,849; and 6,093,383. Exemplarymonoamine, diamide, single thiol chelators stabilized by a mixture of ahydrophilic thioether and a hydrophilic 6-hydroxy chroman have generalformulae selected from the group consisting of:

wherein n, m and p are each integers that are independently 0 or 1; eachR′ is independently H, lower alkyl, C₂-C₄ hydroxyalkyl, or C₂-C₄alkoxyalkyl, and each R is independently H or R″, where R″ is asubstituted lower alkyl group, an unsubstituted lower alkyl group, or aphenyl not comprising a thiol group, and one R or R′ is L, where L is abivalent linker linking the metal chelator to the targeting moiety andwherein when one R′ is L, NR′₂ is an amine. In preferred embodiments, Lis a C₁-C₆ linear alkyl group; a branched chain alkyl group; a cyclicalkyl group; a carboxylic ester; a carboxamide; a sulfonamide; an ether;a thioether; an amine; an alkene; an alkyne; a 1,2-linked, optionallysubstituted benzene ring; a 1,3-linked, optionally substituted benzenering; a 1,4-linked, optionally substituted benzene ring; an amino acid,or a peptide of 2 to about 10 amino acids, or combinations thereof. Inpreferred embodiments, R″ is a C₁-C₆ linear alkyl group; a branchedalkyl group; a cyclic alkyl group; a —C_(q)OC_(r)—, —C_(q)NHC_(r)— or—C_(q)SC_(r)— group, where q and r are integers each independently 1 to5 wherein the sum of q+r is not greater than 6; a (C₁-C₆) alkyl-X, whereX is a hydroxyl group; a substituted amine; a guanidine; an amidine; asubstituted thiol group; a carboxylic acid; an ester; a phosphate group;a sulfate group; a phenyl group; a phenyl group substituted with ahalogen, a hydroxyl, a substituted amine, a guanidine, an amidine, asubstituted thiol, an ether, a phosphate group, or a sulfate group; anindole group; a C₁-C₆ heterocyclic group containing 1 to 3 nitrogen,oxygen or sulfur atoms; or a combination thereof.

In a specific embodiment, the monoamine, diamide single thiol radiometalchelator stabilized in accordance with the invention may have a formula:

wherein R¹ and R² are each independently H, lower alkyl, C₂-C₄hydroxyalkyl, or C₂-C₄ alkoxyalkyl; R³, R⁴, R⁵ and R⁶ are independentlyH, substituted or unsubstituted lower alkyl or phenyl not comprising athiol group; R⁷ and R⁸ are each independently H, lower alkyl, lowerhydroxyalkyl or lower alkoxyalkyl; L is a bivalent linker group and Z isa targeting moiety.

The monoamine, diamide single thiol radiometal chelator stabilized inaccordance with the invention may alternatively have a formula:

wherein R¹ and R² are each independently H, lower alkyl, C₂-C₄hydroxyalkyl, or C₂-C₄ alkoxyalkyl; R³, R⁴, R⁵ and R⁶ are independentlyH, substituted lower alkyl, unsubstituted lower alkyl, phenyl,substituted phenyl not comprising a thiol group, and one of R³, R⁴, R⁵or R⁶ is Z-L-HN(CH₂)_(n)—, where L is a bivalent linker, Z is atargeting moiety, and n is an integer from 1 to 6; R⁷ and R⁸ are eachindependently H, lower alkyl, lower hydroxyalkyl, lower alkoxyalkyl; andX is an amino group, a substituted amino group or —NR¹—Y, where Y is anamino acid, an amino acid amide, or a peptide comprising from 2 to 10amino acids.

The monoamine, diamide single thiol radiometal chelator stabilized inaccordance with the invention may alternatively have a formula:

wherein R¹ and R² are each independently H, lower alkyl, lowerhydroxyalkyl, or lower alkenylalkyl; R³ and R⁴ are independently H,substituted or unsubstituted lower alkyl or phenyl not comprising athiol group; n is an integer from 1 to 6; L is a bivalent linker; and Zis a targeting moiety.

The monoamine, diamide single thiol radiometal chelator stabilized inaccordance with the invention may alternatively have a formula:

wherein L is a bivalent linker and Z is a targeting moiety.

Bisamide bisthiol metal chelators stabilized in accordance with thepresent invention preferably have a formula selected from the groupconsisting of:

wherein

-   -   each R is independently H, CH₃ or C₂H₅;    -   each (pgp)^(S) is independently a thiol protecting group or H;    -   m, n and p are independently 2 or 3;    -   A is linear or cyclic lower alkyl, aryl, heterocyclyl, a        combination thereof or a substituted derivative thereof;

wherein

-   -   each R is independently H, CH₃ or C₂H₅;    -   m, n and p are independently 2 or 3;    -   A is linear or cyclic lower alkyl, aryl, heterocyclyl, a        combination thereof or a substituted derivative thereof;    -   V is H or —CO-peptide;    -   R′ is H or peptide;        and wherein when V is H, R′ is peptide; and when R′ is H, V is        —CO-peptide.

For example, the stabilizers of the invention may be used to increasethe shelf life of radiopharmaceuticals comprising the specificprecursors set forth below:

GGCSIPPEVKFNKPFVYLI · amide; (SEQ ID NO:1) GGCSIPPEVKFNKPFVYLI; (SEQ IDNO:2) GGCGLF; (SEQ ID NO:3) RGCSIPPEVKFNKPFVYLI · amide; (SEQ ID NO:4)RGCGHRPLDKKREEAPSLRPAPPPISGGYR · amide; (SEQ ID NO:5) GGCRPKPQQFFGLM ·amide; (SEQ ID NO:6) GGCFVYLI · amide; (SEQ ID NO:7) (acetyl ·TKPRGG)₂K(ε-K)GC · amide; (SEQ ID NO: 13) F_(D)FYW_(D)KTFT(ε-K)GC ·amide; acetyl · F_(D)FYW_(D)KTFT(ε-K)GC · amide; acetyl · Nal_(D) · Cpa· YW_(D)KTFT(ε-K)GCKK · amide; acetyl · F_(D)FYW_(D)KTFTGGG(ε-K)GC ·amide; acetyl · F_(D)FYW_(D)KTFTGGG(ε-K)KC · amide; acetyl · KKKKK ·Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GC · amide; acetyl · D_(D)F_(D) · Cpa ·YW_(D)KTFT(ε-K)GCKK · amide; acetyl · D_(D)F_(D) · Cpa ·YW_(D)KTC(ε-K)GCKK · amide; acetyl · KKKKK · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCKK · amide; acetyl · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCKK · amide; acetyl-DDD · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCKK · amide; acetyl · D_(D)DF_(D) · Cpa ·YW_(D)KTFT(ε-K)GCKK · amide; (DTPA) · F_(D)FYW_(D)KTFT(ε-K)GC · amide;(DTPA) · Nal_(D) · Cpa · · YW_(D)KT · Nal · T(ε-K)GCKK · amide; (DTPA) ·(ε-K)GCF_(D)FYW_(D)KTFT · amide; (DTPA) · (ε-K)GCF_(D) · Cpa · ·YW_(D)KTFT · amide; (DTPA) · F_(D) · Cpa · YW_(D)KTFT(ε-K)GC · amide;(DTPA) · Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GC · amide; (DTPA) · Aca · F_(D)· Cpa · YW_(D)KTFT(ε-K)GC · amide; (DTPA) · Nal_(D) · Cpa · YW_(D)KT ·Nal · T(ε-K)GCKK · amide; (DTPA) · Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GCKK ·amide; CH₂CO · FFW_(D)KTFC(ε-K)GC · amide; CH₂CO ·FFW_(D)KTFCKKKKK(ε-K)GC · amide; CH₂CO · FFW_(D)KTFC(ε-K)KKKKKGC ·amide; AKCGGGF_(D)FYW_(D)KTFT · amide; AKCGGGF_(D)YW_(D)KTFT · amide;DDDD · Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GCKKKK · amide; DDD · Nal_(D) ·Cpa · YW_(D)KTFT(ε-K)GCKK · amide; Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GCKK ·amide; Trc · Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GCKK · amide; Hca · Nal_(D)· Cpa · YW_(D)KTFT(ε-K)GCKK · amide; (Trc)₂ · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCKK · amide; KKKK · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCDDDD · amide; K_(D) · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCD · amide; K_(D)K · Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GCDD· amide; K_(D)KK · Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GCDDD · amide; K_(D)KK· Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GCDD · amide; K_(D)KKK · Nal_(D) · Cpa· YW_(D)KTFT(ε-K)GCDD · amide; K_(D)KKK · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCKDKD · amide; K_(D)KKKF_(D) · Cpa · YW_(D)KTF,Nal ·(ε-K)GCDDDD · amide; K(BAT) · Nal_(D) · C_(Me)YW_(D)KVC_(Me)T · amideK_(D)DKD · Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GCKDKD · amide; KDKD · Nal_(D)· Cpa · YW_(D)KTFT(ε-K)GCKDKD · amide; F_(D) · Cpa · YW_(D)KTC(ε-K)GCKK· amide; F_(D) · Cpa · YW_(D)KTC(ε-K)GC · amide; F_(D) · Cpa ·YW_(D)KTFT(ε-K)GCKK · amide; F_(D) · Cpa · YW_(D)K · Abu · Nal ·T(ε-K)GC · amide; F_(D) · Cpa · YW_(D)KTFTGGG(ε-K)GC · amide; F_(D) ·Cpa · YW_(D)KTFT(ε-K)GCR · amide; (Trc-imide) · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCR · amide; Trc · (Trc-imide) · K · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCRR · amide; (Trc-imide)₂K · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCRR · amide; (Trc-imide)₂K · Nal_(D) · Cpa ·YW_(D)KTFT(ε-K)GCR · amide; D_(D)DF_(D) · Cpa · YW_(D)KTFT(ε-K)GCKK ·amide; D_(D)F_(D) · Cpa · YW_(D)KTFT(ε-K)GCKK · amide;F_(D)FYW_(D)KTFT(ε-K)GCKK · amide; AKCGGGF_(D)YW_(D)KTFT · amide;(2-ketogulonyl) · Nal_(D) · Cpa · YW_(D)KTFT(ε-K)GCKK · amide;(2-ketogulonyl) · F_(D) · Cpa · YW_(D)KTFT(ε-K)GC · amide; cyclo-(N-CH₃)FYW_(D)KV · Hcy(CH₂CO · GC · Dap · Dap · amide); cyclo-(N-CH₃)FYW_(D)KV · Hcy(CH₂CO · (γ-Dab)KCR · amide); cyclo-(N-CH₃)FYW_(D)KV · Hcy(CH₂CO · KKKKK(ε-K)GC · amide); cyclo-(N-CH₃)FYW_(D)KV · Hcy(CH₂CO) · (ε-K)GCK · amide; cyclo-( N-CH₃)FYW_(D)KV· Hcy(CH₂CO · (β-Dap)KCR · amide); cyclo-( N-CH₃)FYW_(D)KV · Hcy(CH₂CO ·(β-Dap)KGK · amide); cyclo-( N-CH₃)FYW_(D)KV · Hcy(CH₂CO · (δ-Orn)GCK ·amide); cyclo-( N-CH₃)FYW_(D)KV · Hcy(CH₂CO · (β-Dap)GCK · amide);cyclo-( N-CH₃)FYW_(D)KV · Hcy(CH₂CO · K(ε-K)KCK · amide); cyclo-(N-CH₃)FYW_(D)KV · Hcy(CH₂CO · (ε-K)GCKK · amide); cyclo-(N-CH₃)FYW_(D)KV · Hcy(CH₂CO) · K(ε-K)GC · amide; cyclo-( N-CH₃)FYW_(D)KV· Hcy(CH₂CO) · (ε-K)GC · amide; RGCQAPLYKKIIKKLLES; (SEQ ID NO:8) acetyl· KK(ε-K)GCGCGGPLYKKIIKKLLES; acetyl · KKKKKK(ε-K)GCGGPLYKKIIKKLLES;(CH₂CO · Y_(D) · Amp · GDCKGCG · amide)₂(CH₂CO)₂K(ε-K)GC · amide; (CH₂CO· Y_(D) · Amp · GDCGGC_(Acm)GC_(Acm)GGC · amide)₂(CH₂CO)₂K(ε-K)GC ·amide; (CH₂CO · Y_(D) · Apc · GDCKGCG · amide)₂(CH₂CO)₂K(ε-K)GC · amide;{(CH₂CO · Y_(D) · Apc · GDCGGCG · amide)(CH₂CO)}₂K(ε-K)GC · amide;(CH₂CO · Y_(D) · Apc · GDCKGG)₂K(ε-K)GC · β-Ala · amide; (CH₂CO · Y_(D)· Apc · GDCKKG)₂K(ε-K)GC · β-Ala · amide; {(CH₂CO · Y_(D) · Apc ·GDCG)₂KG}₂K(ε-K)GCG · amide; (CH₂CO · Y_(D) · Apc · GDC)₂K(ε-K)GCG ·amide; ({(CH₂CO · Y_(D) · Apc · GDCGGC_(Acm)GC_(Acm)GGC ·amide)(CH₂CO)}₂ · K)₂K(ε-K)GCG · amide; {(CH₂CO · Y_(D) · Apc ·GDCGGC_(Acm)GC_(Acm)GGC · amide)₂(CH₂CO)₂K}₂K(ε-K)GCG · amide; (CH₂CO ·Y_(D) · Apc · GDCGGC_(Acm)GC_(Acm)GGC · amide)₂(CH₂CO)₂K(ε-K)GC · amide;HSDAVFTDNYTRLRKQMAVKKYLNSILN(ε-K)GC · amide; (SEQ ID NO:16)HSDAVFTDNYTRLRKQMAVKKYLNSILNGGC · amide; (SEQ ID NO:9)AGCHSDAVFTDNYTRLRKQMAVKKYLNSILN · amide; (SEQ ID NO:10)HSDAVFTDNYTRLRKQMAVKKYLNSILNC(BAT) · amide; (SEQ ID NO:11) CH₂CO · SNLST· HhcVLGKLSC(BAT)ELHKLQTYPRTNTGSGTP · amide; (SEQ ID NO:12) CH₂CO ·SNLST · HhcVLGKLSQELHKLQTYPRTNTGSGTP(ε-K)GC · amide; (SEQ ID NO:17)CH₂CO · SNLST · HhcVLGKLSC(CH₂CO · GGCK · amide)ELHKLQTYPRTNTGSGTP ·amide; (SEQ ID NO:18) CH₂CO · SNLST · HhcVLGKLSC(CH₂CO · (β-Dap)KCK ·amide)ELHKLQTYPRTNTGSGTP · amide; (SEQ ID NO:19) CH₂CO · SNLST ·HhcVLGKLSC(CH₂CO · (ε-K)GCE · amide)ELHKLQTYPRTNTGSGTP · amide; (SEQ IDNO:20) CH₂CO · SNLST · HcyVLGKLSC(CH₂CO · GGCK ·amide)ELHKLQTYPRTNTGSGTP · amide; (SEQ ID NO:21) CH₂CO · SNLST ·HcyVLGKLSC(CH₂CO · (β-Dap)KCK · amide)ELHKLQTYPRTNTGSGTP · amide; (SEQID NO:22) CH₂CO · SNLST · HcyVLGKLSC(CH₂CO · (ε-K)GCE ·amide)ELHKLQTYPRTNTGSGTP · amide; (SEQ ID NO:23) CH₂CO · SNLST · Cys ·LGKLSC(CH₂CO · GGCK · amide)ELHKLQTYPRTNTGSGTP · amide; (SEQ ID NO:24)CH₂CO · SNLST · CysVLGKLSC(CH₂CO · (β-Dap)KCK · amide)ELHKLQTYPRTNTGSGTP· amide; (SEQ ID NO:25) CH₂CO · SNLST · CysVLGKLSC(CH₂CO · (ε-K)GCE ·amide)ELHKLQTYPRTNTGSGTP · amide; (SEQ ID NO:26) SNLST ·AsuVLGKLSC(CH₂CO · (β-Dap)KCK · amide)ELHKLQTYPRTNTGSGTP · amide; (SEQID NO:27) SNLST · AsuVLGKLSC(CH₂CO · (β-Dap)KCK ·amide)ELHKLQTYPRTDVGAGTP · amide; (SEQ ID NO:28)cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Tyr-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Phe(4-F)-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Phe(4-NH₂)-Cys-Thr-Ser);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Dab-Cys-Thr);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Phe(4-NH₂)-Cys-Thr);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Phe(4-NH₂)-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-His-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Arg-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Gly-Cys-Lys-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Ser-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Dab-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Gly-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Dab-Cys-Ser(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Gly-Gly-Cys-Lys-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Gly-Gly-Cys-Arg-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Ser-Ser-Cys-Lys-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Ser-Ser-Cys-Arg-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Ser-Ser-Cys-Lys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Ser-Ser-Cys-Dap-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Ser-Ser-Cys-NH(CH₂CH₂O)₂CH₂CH₂NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Ser-Cys-Thr-NH(CH₂CH₂O)₂CH₂CH₂NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Gly-Lys-Cys-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Ser-Lys-Cys-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Lys-Gly-Cys-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Ser-Dab-Cys-Ser(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Ser-Dap-Cys-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Gly-Gly-Cys-His-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Gly-Gly-Cys-Phe(4-NH₂)-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Orn-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Dap-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Lys-Cys-Thr(ol));cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Ser-Ser-Cys-NHCH₂CH₂OCH₂CH₂NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-β-Dap-Lys-Cys-NH₂);cyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-δ-Orn-Gly-Cys-NH₂); andcyclo-Tyr-D-Trp-Lys-Thr-Phe-(N-CH₃)Hcy(CH₂CO-Thr-Gly-Gly-Cys-NH₂) ·

Single-letter and three-letter abbreviations for amino acids can befound in G. Zubay, Biochemistry (2d. ed.), 1988 (MacMillan Publishing:New York) p.33; other abbreviations are as follows: Acm isacetamidomethyl; Mob is 4-methoxybenzyl; Abu is aminobutyric acid; F_(D)is D-phenylalanine; W_(D) is D-tryptophan; Y_(D) is D-tyrosine; Aca is6-aminohexanoic acid; Apc is S-(3-aminopropyl)cysteine; Hcy ishomocysteine; Nal is 2-naphthylalanine; Cpa is 4-chlorophenylalanine;K_(D) is D-lysine; D_(D) is D-aspartate; Nal_(D) is D-2-naphthylalanine;DTPA is diethylenetriaminepentaacetic acid; Trc is tricarballylic acid;Trc-imide is tricarballylic imide; and Hca is hexacarboxycyclohexane. (. . . )₂K represents covalent linkage to both amino groups of lysine.Hcy( . . . ) represents covalent linkage to the sidechain sulfur atom ofhomocysteine. (N—CH₃)F represents N-α-methyl-phenylalanine. Underliningbetween groups (e.g., as between the CH₂CO. group and cysteine (C) inCH₂CO.Y_(D)RGDC) represents a cyclic sulfide. Underlining between aminoacids (e.g., as between the cysteines (C) in CNPRGDC (SEQ ID NO:29))represents a cyclic disulfide bond. The term “cyclo” before anunderlined sequence means an N-terminus-to-C-terminus cyclic sequence.The subscript X_(D) indicates the amino acid is in the D-configuration;all other subscripts refer to amino acid sidechain protecting groups.ε-K, δ-Orn, γ-Dab, and β-Dap are defined as set forth above. Asu is2-amino suberic acid, wherein the amino terminal amino acids of peptidescontaining an Asu residue are cyclized via an amide bond between theamino terminal amino group and the side chain carboxylic acid moiety ofthe Asu residue. BAT isN⁶,N⁹-bis(2-mercapto-2-methylpropyl)-6,9-diazanonanoic acid.

In addition, a hydrophilic 6-hydroxy-chroman derivative may be used inaccordance with the present invention to stabilize labelledradiopharmaceutical precursors comprising a benzodiazepine derivative,such as those described in U.S. Pat. No. 6,171,578. In a preferredembodiment, a hydrophilic 6-hydroxy-chroman derivative such as6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid is used tostabilize radiolabelled1-[(carboxyglycyl-glycyl-glycyl-cysteinamide)methyl]-4-(2-carboxyethyl)-7-[(4-amidinophenyl)methyl]3,4-dihydro-1H-1,4-benzodiazepine-2,5-dionetrifluoroacetate.

In addition, hydrophilic 6-hydroxy-chroman dervative may be used inaccordance with the present invention to stabilize labelledradiopharmaceutical precursors comprising a targeting moiety or domaincovalently linked to the known chelators1,4,7,10-tetraazadodecanetetraacetic acid and derivatives thereof:

where n is an integer that is 2 or 3 and where each R is independentlyH, C₁ to C₄ alkyl, or aryl and one R is covalently linked to thetargeting moiety, and desferrioxamine.

A radiopharmaceutical comprising any radionuclide or radiometal may bestabilized in accordance with the present invention. For example,radiopharmaceuticals containing such nuclides as ¹²⁵I, ¹³¹I, ²¹¹At,⁴⁷SC, ⁶⁷Cu, ⁷²Ga, ⁹⁰Y, ¹⁵³Sm, ¹⁵⁹Gd, ¹⁶⁵Dy, ¹⁶⁶Ho, ¹⁷⁵Yb, ¹⁷⁷Lu, ¹⁸⁶Re,¹⁸⁸Re, ²¹²Bi, ²¹³Bi, ⁶⁸Ga, ^(99m)Tc, ¹¹¹In, and ¹²³I, and the like maybe stabilized by addition of a hydrophilic 6-hydroxy chroman derivativein accordance with the invention. The extent of stabilization of aparticular radiopharmaceutical precursor when chelated to differentradionuclides may vary. For example, a ^(99m)Tc-labelled precursor maybe stabilized to a greater extent than a ¹⁸⁸Re-labelled form of the sameprecursor.

The compositions of the invention are formulated as a sterile,pyrogen-free, parenterally acceptable aqueous solution which mayoptionally be supplied in lyophilized form and be reconstituted by theuser. The compositions of the invention may be provided as components ofkits which may include buffers, additional vials, instructions for use,and the like.

The pharmaceutical compositions of the invention comprises aradiopharmaceutical precursor in combination with a stabilizing amountof a hydrophilic 6-hydroxy-chroman, optionally with a pharmaceuticallyacceptable diluent or a carrier such as species appropriate albumin. Asused herein, a “pharmaceutically acceptable diluent or carrier” mayinclude any and all solvents, dispersion media, antibacterial andantifungal agents, isotonic agents, enzyme inhibitors, transfer ligandssuch as glucoheptonate, tartrate, citrate, or mannitol, and the like.The use of such media and agents for pharmaceutically active substancesis well known in the art. For example, Sodium Chloride Injection andRinger's Injection are commonly used as diluents. The preparation ofsuch parenterally acceptable solutions, having due regard to pH,isotonicity, stability, and the like, is within the skill in the art.

In accordance with the method of this invention, radiopharmaceuticalsare preferably administered intravenously in a single unit dose, eithertotally as a bolus or partly as a bolus followed by infusion over 1-2hours. The amount of solution to be injected at unit dosage is fromabout 0.01 mL to about 10 mL, containing about 0.01 mCi to about 100 mCiof radioactivity, preferably from about 1 mCi to about 50 mCi. Theamount of the radiopharmaceutical in the unit dose may range from about0.1 to about 10 mg/kg body weight, After intravenous administration, thesite is monitored, for example, by radioimaging in vivo if theradiopharmaceutical is a diagnostic agent.

The following examples are shown by way of illustration and not beconsidered as limitations.

EXAMPLE 1 Effect of Gentisic Acid on Radiochemical Purity of^(99m)Tc-Labelled Depreotide

Gentisic acid (GA) was tested for its ability to stabilize the^(99m)Tc-labelled somatostatin receptor-binding peptide depreotide,which has the structure.

This peptide is represented as:cyclo(N—CH₃)FYW_(D)KV.Hcy.(CH₂CO.(β-Dap)KCK.amide)in the listing set forth above.

Lyophilized kit vials were prepared containing depreotide, GA, and othercomponents as described in Table 1. Formulations were adjusted to pH 7.4or 8.5 (as noted) prior to lyophilization.

TABLE 1 Component Control GA I GA II GA III Depreotide  50 μg  50 μg  50μg  50 μg Sodium Glucoheptonate  25 mg  25 mg  5 mg  25 mg Dihydrate¹Edetate Disodium 100 μg 100 μg 100 μg 100 μg Dihydrate² StannousChloride  50 μg  50 μg  50 μg  50 μg Dihydrate³ Gentisic Acid Sodium — 1 mg  1 mg  1 mg Salt Hydrate⁴ pH 7.4 7.4 7.4 8.5 ¹PfanstiehlLaboratories, Waukegan, Illinois, USA. ²J. T. Baker, Phillipsburg, NewJersey, USA. ³Acros Organics/Fisher Scientific, Pittsburgh,Pennsylvania, USA. ⁴Sigma Chemical Co., St. Louis, Missouri, USA.The lyophilized kits were radiolabelled with ^(99m)Tc by reconstitutionwith 1.0 mL technetium ^(99m)Tc sodium pertechnetate (Technelite®Molybdenum Mo99-Technetium Tc99m Generator, DuPont, Billerica, Mass.)containing approximately 50 mCi ^(99m)Tc and heating in a boiling waterbath for 10 minutes. Radiolabelling yield (RCP) results as measured byreversed phase HPLC are given in Table 2.

TABLE 2 HPLC RCP (%) Formulation 0.5 hr 3.5 hr 6.5 hr Control 94.5 88.386.4 94.2 92.1 90.8 94.5 91.7 90.1 (Average ± 1SD): (94.4 ± 0.2) (90.7 ±2.1) (89.1 ± 2.4) GA I 82.4 79.4 77.2 GA II 29.1 25.1 20.5 GA III  0.9 0.7  0.6These results indicate that gentisic acid decreases the radiolabellingyield and the stability of ^(99m)Tc-depreotide when included informulated kits.

EXAMPLE 2 Stabilization of ^(99m)Tc-Labelled Depreotide by Trolox®

Lyophilized kit vials were prepared containing depreotide, Trolox®, andother components as described in Table 3. All formulations were adjustedto pH 7.4 prior to lyophilization.

TABLE 3 Component Control Trolox I Trolox II Trolox III Trolox IVDepreotide  50 μg   50 μg  50 μg  50 μg  50 μg Sodium  5 mg   5 mg  5 mg 5 mg  5 mg Glucoheptonate Dihydrate Edetate 100 μg  100 μg 100 μg 100μg 100 μg Disodium Dihydrate Stannous  50 μg   50 μg  50 μg  50 μg  50μg Chloride Dihydrate Trolox —  0.6 mg  1 mg  2 mg  5 mgThe lyophilized kits were radiolabelled with ^(99m)Tc by reconstitutionwith 1.0 mL technetium ^(99m)Tc sodium pertechnetate (Technelite®)containing approximately 50 mCi ^(99m)Tc and incubation at roomtemperature for 30 minutes following reconstitution. Some of theformulations were also radiolabelled in a heated preparation (heat in aboiling water bath for 10 minutes). Radiolabelling yield (RCP) resultsas measured by reversed phase HPLC are given in Table 4.

TABLE 4 HPLC RCP (%) Formulation Prep Type 0.5 hr 3.5 hr 6.5 hr ControlHeated 92.0 85.9 84.5 Heated 91.4 85.3 78.3 (Average): (91.7) (85.6)(81.5) Rm Temp 92.0 85.0 84.2 Rm Temp 92.6 85.2 80.7 Rm Temp 92.0 81.479.5 Rm Temp 89.5 82.8 — (Average ± 1SD): (91.5 ± 1.4) (83.6 ± 1.8)(81.5 ± 2.4) Trolox I (600 μg) Rm Temp 94.3 93.2 92.0 Rm Temp 91.8 88.689.1 (Average): (93.1) (90.9) (90.6) Trolox II (1 mg) Rm Temp 91.3 89.691.0 Rm Temp 92.9 91.8 92.5 Rm Temp 94.1 93.2 91.1 (Average ± 1SD):(92.8 ± 1.4) (91.5 ± 1.8) (91.5 ± 0.8) Trolox III (2 mg) Heated 94.991.1 85.6 Heated 95.3 92.9 88.7 (Average): (95.1) (92.0) (87.2) Rm Temp95.4 94.8 95.4 Rm Temp 94.5 93.7 93.8 Rm Temp 95.5 — 92.2 Rm Temp 93.891.7 92.4 Rm Temp 94.8 92.4 93.0 Rm Temp — 94.6 93.5 (Average ± 1SD):(94.8 ± 0.7) (93.4 ± 1.4) (93.4 ± 1.2) Trolox IV (5 mg) Rm Temp 93.392.0 — Rm Temp 92.1 94.8 93.8 (Average): (92.7) (93.4) (93.8)These results indicate that Trolox® increases the radiolabelling yieldand the stability of ^(99m)Tc depreotide prepared from formulated kits.

EXAMPLE 3 Stabilization of ^(99m)Tc Depreotide by Trolox® in LyophilizedKit Preparations; Accelerated Temperature (40° C.) Storage

Lyophilized kits were prepared containing depreotide, Trolox®, and othercomponents as described in Table 5. All formulations were adjusted to pH7.4 prior to lyophilization. The kits were stored for one week at 40° C.Some kits were also stored at −10° C. as controls.

TABLE 5 Component Control Trolox Depreotide  50 μg  50 μg SodiumGlucoheptonate Dihydrate  5 mg  5 mg Edetate Disodium Dihydrate 100 μg100 μg Stannous Chloride Dihydrate  50 μg  50 μg Trolox ® —  2 mgThe lyophilized kits were radiolabelled with ^(99m)Tc by reconstitutionwith 1.0 mL technetium ^(99m)Tc sodium pertechnetate (Technelite®)containing approximately 50 mCi ^(99m)Tc and incubation either at roomtemperature (30 minutes) or in a boiling water bath (10 min).Radiolabelling yield (RCP) results as measured by reversed phase HPLCare given in Table 6.

TABLE 6 HPLC RCP (%) Formulation Storage Temp Prep Type 0.5 hr 3.5 hr6.5 hr Control −10° C. Heated — 82.6 77.8   40° C. Heated — 82.6 79.0Trolox ® −10° C. Rm Temp 94.4 92.9 92.3   40° C. Rm Temp 86.6 89.2 88.6These results indicate that the Trolox® stabilizes ^(99m)Tc-depreotideprepared from lyophilized kits which had been thermally stressed underconditions of accelerated temperature storage.

EXAMPLE 4 Stabilization of a ^(99m)Tc-Labelled Peptide by Trolox

Trolox® was tested for its ability to stabilize a ^(99m)Tc-labelledglycoprotein IIb/IIIa receptor-binding peptide having the structure.

This peptide is represented as:(CH₂CO.Y_(D).Amp.GDC.KGCG.amide)₂(CH₂CO)₂K(ε-K)GC.amidein the listing set forth above.

Lyophilized kit vials were prepared containing the peptide (50 μg),sodium glucoheptonate dihydrate (10 mg), stannous chloride dihydrate (50μg), and edetate disodium dihydrate (100 μg). The formulation wasadjusted to pH 7.4 prior to lyophilization.

The lyophilized kits were radiolabelled with ^(99m)Tc in the presenceand absence of Trolox®. To the Trolox® preparation was added 2 mgTrolox® in 100 μL ethanol and 100 μL saline. The ethanol was necessaryto aid in the dissolution of the Trolox®. To the control preparation wasadded 100 μL ethanol and 100 μL saline to account for the additionalsaline or ethanol added with the Trolox. Both vials were thenreconstituted with 1.0 mL technetium ^(99m)Tc sodium pertechnetate(Technelite®) containing approximately 50 mCi ^(99m)Tc and allowed toincubate for 30 minutes at room temperature. Radiolabelling yield (RCP)results as measured by reversed phase HPLC are given in Table 7.

TABLE 7 HPLC RCP (%) Preparation 0.5 hr 3.5 hr 6.5 hr Control 91.8 80.476.2 Trolox ® (2 mg) 89.5 91.9 92.9These results show that Trolox® increases the radiolabelling yield andthe stability of ^(99m)Tc-peptide.

EXAMPLE 5 Stabilization of ^(99m)Tc-Labelled Peptide Chelator by Trolox®

Trolox® was tested for its ability to stabilize a ^(99m)Tc-labelledmonoamine, diamide, single thiol peptide chelator having the structure.

N-3-benzoyl-2,3-(S)-diaminopropionyl-L-lysinyl-L-cysteinyl-L-lysinylamide

Lyophilized kit “placebo” vials were prepared containing sodiumglucoheptonate dihydrate, edetate disodium dihydrate, and stannouschloride dihydrate at the concentrations set forth in Table 1 (controlformulation).

The peptide chelator was radiolabelled with ^(99m)Tc in the presence andabsence of Trolox®. The peptide chelator was dissolved in water at aconcentration of 1 mg/mL, and 50 μg (50 μL) of the peptide was added toeach of three placebo vials. Ethanol and Trolox® were added to thecontrol and Trolox®, preparations as described in Example 11. Inaddition, 100 μL phosphate buffered saline (PBS) was added to eachpreparation. The vials were reconstituted with 0.9-1.0 mL ^(99m)Tcsodium pertechnetate (Technelite®) containing approximately 50 mCi^(99m)Tc, and heated in a boiling water bath for ten minutes.Radiolabelling yield (RCP) results as measured by reversed phase HPLCare given in Table 8.

TABLE 8 HPLC RCP (%) Preparation 0.5 hr 3 hr 6 hr 9 hr Control 94.1 92.485.9 80.0 Trolox ® (2 mg) 95.3 95.4 91.5 86.4These results show that Trolox® increases the radiolabelling yield andthe stability of a ^(99m)Tc-labelled peptide chelator.

EXAMPLE 6 Stabilization of a ^(99m)Tc Bisamide Bisthiol Chelator byTrolox®

Trolox® was tested for its ability to stabilize a ^(99m)Tc-labellednon-peptide chelator (4-(butanoic acid)-2,2,9,9tetramethyl-4,7-diaza-1,10-decanedithiol) having the structure.

The non-peptide chelator was radiolabelled with ^(99m)Tc in the presenceand absence of Trolox® using the placebo vial heated preparationprocedure as described in Example 4. Radiolabelling yield (RCP) resultsas measured by reversed phase HPLC are given in Table 9.

TABLE 9 HPLC RCP (%) Preparation 0.5 hr 3 hr 6 hr 9 hr Control 48.5 56.554.0 52.9 Trolox ® (2 mg) 88.6 79.1 78.3 77.0These results show that Trolox® increases the radiolabelling yield andthe stability of a ^(99m)Tc-labelled non-peptide chelator.

It should be understood that the foregoing disclosure emphasizes certainspecific embodiments of the invention and that all modifications orequivalents thereto are within the spirit and scope of the invention asset forth in the appended claims.

1. A composition comprising: (1) a radiopharmaceutical precursorcomprising a chelator not covalently linked to a targeting moiety ordomain; and (2) a stabilizing amount of a hydrophilic 6-hydroxy-chromanderivative of the formula:

wherein one of Y or Z is selected from the group consisting of O, S,C═O, and (CHR³)_(n), where n is an integer from 0 to 3, and the other ofY or Z is selected from the group consisting of C═O and (CHR³)_(n) wheren is an integer from 0 to 3; each R³ group is independently selectedfrom the group consisting of H, alkyl, halogen, —OR⁴, —SO₃H, —SO₃R⁴,—S(O)_(m)R⁴, —COOR⁴, —NO₂, —CONH_(m)(R⁴)_(2-m), —NH_(m)(R⁴)_(2-m),—COR⁴, —CH₂OR⁴, —COR⁵, —SO₂NH_(m)(R⁴)_(2-m), —R⁵, and —CH₂R⁵, where m isan integer from 0 to 2; R⁴ is H or C₁ to C₃ alkyl; and R⁵ is selectedfrom the group consisting of a monosaccharide, disaccharide, and ahydrophilic peptide sequence of up to 5 amino acids comprising at leastone hydrophilic amino acid residue.
 2. The composition of claim 1wherein, in the formula, both Y and Z are —CH₂—.
 3. The composition ofclaim 1, wherein the hydrophilic 6-hydroxy-chroman is selected from thegroup consisting of 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylicacid, 6-hydroxy-2,5 7,8-tetramethylchroman-2-carboxylic acid-4-sulfonicacid, 6-hydroxy-2,5,7,8-tetramethylchroman-3-hydroxy-2-carboxylic acid,6-hydroxy-2,5,7,8-tetramethylchroman-2-glucosamine and6-hydroxy-2,5,7,8-tetramethylchroman-2-(carboxy-seryl-seryl-serylamide).4. The composition of claim 3, wherein the hydrophilic 6-hydroxy-chromanis 6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylic acid.
 5. Thecomposition of claim 1, wherein the precursor comprises maGGG.
 6. Thecomposition of claim 1, wherein the precursor comprises a peptidechelator.
 7. The composition of claim 1, wherein the precursor comprisesa non-peptide chelator.
 8. The composition of claim 1, furthercomprising a radionuclide.
 9. The composition of claim 8, wherein theradionuclide is selected from the group consisting of ¹²⁵I, ¹³¹I, ²¹¹At,⁴⁷Sc, ⁶⁷Cu, ⁷²Ga, ⁹⁰Y, ¹⁵³Sm, ¹⁵⁹Gd, ¹⁶⁵Dy, ¹⁶⁶Ho, ¹⁷⁵Yb, ¹⁷⁷Lu, ¹⁸⁶Re,¹⁸⁸Re, ²¹²Bi, ²¹³Bi, ⁶⁸Ga, ^(99m)Tc, ¹¹¹In and ¹²³I.
 10. The compositionof claim 9, wherein the radionuclide is ^(99m)Tc.
 11. The composition ofclaims 9 or 10, wherein the 6-hydroxy-chroman is 6-hydroxy-2,57,8-tetramethylchroman-2-carboxylic acid.
 12. A method of stabilizing aradiopharmaceutical comprising the steps of: a) providing aradiopharmaceutical precursor comprising a chelator not covalentlylinked to a targeting moiety or domain; b) combining said precursor witha stabilizing amount of a hydrophilic 6-hydroxy-chroman derivativeaccording to claim 1 in a container; and c) adding a radionuclide to thecontainer.
 13. The method of claim 12, wherein the hydrophilic6-hydroxy-chroman is selected from the group consisting of6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid,6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid-4-sulfonic acid,6-hydroxy-2,5,7,8-tetramethylchroman-3-hydroxy-2-carboxylic acid,6-hydroxy-2,5,7,8-tetramethylchroman-2-glucosamine and6-hydroxy-2,5,7,8-tetramethylchroman-2-(carboxy-seryl-seryl-serylamide).14. The method of claim 13, wherein the hydrophilic 6-hydroxy-chromanderivative is 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid.15. The method of claim 12, wherein the radionuclide is ^(99m)Tc. 16.The method of claim 12, wherein the precursor comprises maGGG.
 17. Themethod of claim 12, wherein the precursor comprises a peptide chelator.18. The method of claim 12, wherein the precursor comprises anon-peptide chelator.
 19. A kit comprising a sealed vial containing: (1)a predetermined quantity of a radiopharmaceutical precursor comprising achelator not covalently linked to a targeting moiety or domain; and (2)a stabilizing amount of a hydrophilic 6-hydroxy-chroman derivativeaccording to claim
 1. 20. The kit of claim 19, wherein the hydrophilic6-hydroxy-chroman is 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylicacid.
 21. The kit of claims 19 or 20, wherein the precursor comprisesmaGGG.